Document Evz24N5GZBxKBV0aeRyMYDN5V

tile, but 920-29. t) for all the lung greed on Is do not with the ides. risk for ;on, MD led Jospital, Sweden J Ind Med sotile. Am i a railroad American Journal of Industrial Medicine 15: 353-356 (1989) LETTER TO THE EDITOR Response to Dr. C.-G. Ohlson Key words: asbestos, railroad workers, mesothelioma, lung disease With reference to Ohlson's first comment [1989] concerning the description of asbestos exposure, he says "it is stated that the machinists were almost `exclusively, if not solely' exposed to chrysotile." A more careful reading of my paper [Mancuso, 1988, p 641] would show the text as follows: "From the evaluation of the data relative to the type of asbestos, year and amount and the time period use of various types of asbestos, it is reasonable to conclude that the type of asbestos used for the lagging insulation for the steam locomotives for railroad company A was almost exclusively, if not solely chrysotile, during the 1920-29 period." That statement in the text was preceded by two paragraphs. The first empha sized the lagging operation: "In terms of historical perspective of exposure to asbestos in the railroad industry, the principal and most extensive exposure in volume and dimensions occurred in the application and removal of asbestos lagging on the boilers of steam locomotives." A description of these work practices was provided in Mancuso [1983], Chrysotile was the type of asbestos used since the first application of asbestos in the steam locomotive era for the lagging, and this continued through the succeeding decades. In the next paragraph, it is acknowledged that there was a potential of other forms of asbestos being used in other parts of the locomotive: "In addition to chrysotile, if some other potential exposure to amosite or crocidolite as packing or other material occurred at some point in time, the actual exposure would have been comparatively limited in nature and scope." The article clearly refers to lagging and removal of lagging asbestos as the principal and by far the most extensive exposure in terms of volume and dimensions. The boilers were usually 30-35 feet long, with a diameter of 7 or 8 feet. The asbestos lagging used was approximately 4 feet long, 4 inches thick, and 6 inches wide applied as blocks. For a 30 foot boiler, approximately 375 blocks of that asbestos insulation would be used for the outside of the boiler alone. With these dimensions, assuming 24 pounds to a cubic foot, this would represent approximately 6,000 pounds of asbestos insulation material. In the work practices described [Mancuso, 1983], asbestos exposure in the removal of the lagging was very great indeed, sometimes literally a "snow storm," as when huge chunks of asbestos lagging, tossed from a height of 10-25 feet into lagging wagons, created an enormous amount of dust. This Address reprint requests to Dr. Thomas F. Mancuso, Professor Emeritus, Department of Industrial Environmental Health Sciences, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261. Accepted for publication August 12, 1988. 1989 Alan R. Liss, Inc. ers, on the ilysis of six scrap; my irs, appeari did not in de the shop rking areas is relevant lifferent in nation, and population c g the )tained for . long span :n hired in since this f exposure a specific during the id already Vithin the tablished; /ears was orts were therefore, hort were ja` were iu je of 1983] for 1984]: is-related ossibility case was 1 in years hich five oted that in every amounts os. This decades, he most indicate ; United Response to Dr. Ohlson 355 States in 1920-1930 and 1931-1939, and this limited amount of fiber was never used for insulation (according to the largest manufacturer of asbestos products) but only for such special items as valve packings and braid. This was recognized by Hueper [1965], "Chrysotile furnishes the chief cause of asbestos pneumoconiosis and cancer, especially in the United States because contact with amosite and crocidolite have been comparatively minor, and these varieties represent a small fraction of the total amount of asbestos produced and used." It is inappropriate to compare the amounts and purposes of different types of asbestos that may have been used for insulation in Sweden with what has occurred in the United States, in particular for the study years designated in my railroad study. The railroad facility for the Mancuso study of cohorts of machinists and other crafts was considered one of the largest railroad heavy duty overhaul shops in the world. The Ohson comment ``even small amounts of amphiboles would have been sufficient to explain the occurrence of the mesotheliomas due to the high durability of the amphiboles and low durability of chrysotile in the lungs" is misleading. As cited in my text, Sebastien et al. [1980] have demonstrated that chrysotile has a predilec tion for the pleura; in their amphibole studies this tended to be found in the lungs, and chrysotile was found in the pleura. Within this context, more recently, Churg [1988, p 237] commented on this aspect relative to the lung burden and made several points: 1) chrysotile itself does not accumulate in the lung to any great extent (it is more readily dissolved in vivo compared with amphiboles); 2) this does not mean that only amphiboles are causing disease; 3) it would be most inappropriate for anyone to conclude that just because the lung burden was considerably less, for example, among cases of asbestosis than in a matched series of mesotheliomas, that chrysotile does not cause asbestosis; 4) these data on lung burden do indicate that chrysotile is a poor marker of the amount of chrysotile exposure; and 5) it is incorrect to conclude that chrysotile plays no role in mesothelioma. Indeed, Churg and his colleagues [1984] recently reported that in a consecutive series of 90 autopsies of Quebec chrysotile miners and millers, six deaths were from pleural mesothelioma. The premise of an agreed (?) latent period is questionable. Latent periods, observed in the various cohorts reported, are a reflection on the definition time of the cohorts and the period of follow-up. The Mancuso study, by the very nature of its design, had a much longer period of follow-up. The reality is that chrysotile causes mesothelioma and that the risk is much higher than had been previously appreciated, in addition to its widely acknowledged risk for other asbestos-associated diseases including the most common of all asbestos neoplasms, lung cancer [McDonald and Liddell, 1979; Dement et al., 1983], Thomas F. Mancuso, MD Department of Industrial Environmental Health Sciences, University of Pittsburgh, Pittsburgh, PA 15261 REFERENCES Churg A (1988): Reply to Dr. Dunnigan. Am J Ind Med 14:235-238. Churg A, Wiggs B, DePaoli L, Kampe B, Stevens B (1984): Lung asbestos content in chrysotile workers with mesothelioma. Am Rev Respir Dis 130:1042-1045. 356 Mancuso Dement JM, Harris RL Jr, Symons MJ, Shy CM (1983): Exposures and mortality among chrysotile asbestos workers. Part II: Mortality. Am J Ind Med 12:81-86. Hemberg S (1983): Fact and fiction in occupational epidemiology. The 1982 Lucas Lecture. J R Coll Phys 17:139-143. Hueper WC (1965): Occupational and non-occupational exposure to asbestos. Ann NY Acad Sci 132:41-44. ; Mancuso TF (1983): Mesothelioma among machinists in railroad and other industries. Am J Ind Med 4:501-513. . Mancuso TF (1988): Relative risk of mesothelioma among railroad machinists exposed to chrysotile. Am J Ind Med 13:639-657. McDonald JC, Liddell FDK (1979): Mortality in Canadian miners and millers exposed to chrysotile. Ann NY Acad Sci 330:1-10. Ohlson C-G (1989): Is chrysotile a significant risk factor for mesothelioma? Letter to the Editor. Am J Ind Med 15 (in press). Ohlson C-G, Klaesson B, Hogstedt C (1984): Mortality among asbestos-exposed workers in a railroad workshop. Scand J Work Environ Health 10:283-291. Sebastien P, Janson X, Faudichet A, Hirsch A, Bignon J (1980): Asbestos retention in human respiratory tissues: Comparative measurements in lung parenchyma and in the parietal pleura. In Wagner JC (ed): "Biological Effects of Mineral Fibres." Lyon: IARC Sci Pub, Vol 30, pp 237-246. Selikoff U, Hammond EC, Seidman H (1980): Latency of asbestos disease among insulation workers in the United States and Canada. Cancer 46:2736-2740.